Fluid indicator for hydraulic braking systems



July 20, 1954 Filed Jan. 24, 1952 J. s. KILPATRICK 2,684,414

FLUID INDICATOR F'QR HYDRAULIC BRAKING SYSTEMS 2 Sheets-Sheet 1' July 20, 1954 J. s. KILPATRICK 2,684,414

FLUID INDICATOR FOR HYDRAULIC BRAKING SYSTEMS 2 Sheets-Sheet 2 Filed Jan. 24, 1952 4- Ef'd 5.

6a 1 9 7667 Hr 75 IN VEN TOR.

A r TOR/v5 ys Patented July 20, 1954 iiATENT OFFICE FLUID INDICATOR FDR HYDRAULIC BRAKING SYSTEMS James S. Kilpatrick, Jacksonville, Fla.

Application January 24, 1952, Serial No. 267,999

2 Claims. l

The present invention relates to an improved automatically operable signal device arranged to be associated with the hydraulic braking system of a motor vehicle or the like, to indicate when the brake iiuid reaches a predetermined low level.

An important object is to provide a simple, eiiicient, compact and economical float assembly arranged to be operatively connected to a signal device such as a light on the dash of the vehicle, to indicate when the brake nuid in the braking system becomes low in order to insure the safe operation and the maintenance. ci an adequate supply oi brake fluid at all times.

Other objects and advantages of the invention will be apparent from the following description when taken in conjunction with the accompanying claims and drawings:

Referring to the drawings wherein is disclosed several preferred embodiments, the invention may assume:

Figure l is a side View with parts in section oi a master brake cylinder showing the improved float assembly associated therewith;

Figure 2 is a vertical sectional view of a inedined form oi the invention;

Figure 3 is an electrical diagram of the wire connections;

Figure 4 is an exploded view showing parts of the float assembly, and

Figure 5 is a vertical sectional View of a further modification.

Referring to the drawings, lo designates the master cylinder housing of a conventional hydraulically operated brake system which may be connected to a motor vehicle or the like by the retaining bolts i! which extend through openings in the spaced flanges at one end of the housing so as to be iirmly secured to the inside of the dash i3 or other part ci the vehicle. A recirprocating piston rod is extends into the piston cylinder l5 and is connected with the brake pedal in the usual manner. A transverse partition l separates the cylinder It from the chamber or brake fluid reservoir il. The fluid is free to iiow from the chamber ll into the cylinder l5 through a port i8 in the partition l 6.

The top le of the cylinder lil is provided with a threaded opening 2t which is closed by plug 2l having a reduced externally threaded portion 22 that engages the threaded wall of the opening 2t. The plug il is also formed with an annular collar or stop flange 23 and a reduced polygonal tool receiving portion 2li which encloses the centrally disposed vertical opening 2s and terminates in an annular externally threaded collar or boss 26 that extends upwardly therefrom (Fig. 4). Arranged to be submerged in the brake fluid 2l in the chamber il is a hollow float 28 made or any suitable light durable metal or the like. Extending through the opening 2%3 is a shaft or stein 29 of such length as to project downwardly into the chamber il so as to have its lower threaded end it connected to the threaded end oi a central opening l in the noat 28 (Fig. e). A combined stop and baiile in the form oi an annular collar Si is non-rotatably connected to the shaft 2i; within the chamber i? so as to limit the upward axial movement oi the shaft. The upper end of the shaft 29 extends a limited distance above the top of the plug 2i and is provided with an annular flange or disk 32 that constitutes a combined movable electrical contact and stop. The top of the plug 2i is provided with an enlarged recess 33 which communicates with the opening 25 and is concentric therewith. A nietal bushing or sleeve 34 is arranged to be positioned within the recess 33 so that the shaft 29 may extend loosely therethrough. The bushing 3d has extending radially and outwardly therefrom above the plug 2l a metal arm to which a lead Wire 38 may be detachably connected as at 3l (Fig. l). A tubular insulated member or sleeve 3S is positioned in the recess 33 between the wall thereof and the bushing 34. A fixed contact 39 extends upwardly from the top ci the plug 2l so as to be positioned in the path oi the contact 32 when the latter is moved downwardly. A removable cylindrical cap or cover is preferably provided with an internally threaded lower end portion l (Fig. 1) for engaging the coinplementary threads on the collar so as to enclose and protect the movable Contact 32, stationa-ry contact 39 and their associated parts when the noat assembly is set up. ''he cap de is provided on one side thereof with an opening l2 (Fig. fl) through which extends the contact arm 35. The ilexible wire 36 is connected to one terminal of a lamp socket t3 (Fig. 3) which may be conveniently positioned on the dash adjacent the seat of the driver. A lead wire lll connects the other terminal of the lamp socket @il and may be provided with a manually operable switch 45. The lead wire 44 is connected to a battery l and the ground lll. The lead 3B is similarly grounded through the cylinder Il) and the lead t8. Between the flange 23 and the top of the cylinder le a rubber gasket 49 may be provided in order to form a tight seal when the parts are assembled.

3 t will be seen that the neat assembly is mounted on the plug 2l and is enclosed by the cap Ll so as to provide a unitary and compact structure which may be readily connected or removed from the cylinder lil.

It will be seen that in normal operation the brake iiuid 2l in the chamber iii will assume a level as indicated in Fig. l so that the float it will maintain the shaft 29 in its upward position and the movable contact 32 will be spaced from the fixed contact Eli. When the brake fluid recedes to a predetermined low level or danger marx as indicated by the dotted line position t@ of the iloat (Fig. l), the downward movement of the shalt 23 brings the contact 32 in engagement with the xed contact 39 thus closing an electrical circuit to the light il?, on the dash or the vehicle so as to indicate to the driver or operator that the brake iluid should promptly be replenished in order to avoid the danger oi faulty or inadequate brakes.

n the lnodied form of the invention shown in ig. 2, the removable plug i is arranged to close the opening 52 in the top of the master brake cylinder 5S. The plug 5i has a vertical through opening 5 through which loosely extends a reciprocating shaft te provided with axially spaced lower and upper flanges or collars 5t and respectively, between which is slidably mounted on the shaft, the hollow i'ioat E3 that normally floats on the brake iuid t in the chainber E@ so as to assume the position as shown. rlhs top of the plug 5l may be provided with a polygonal tool engaging portion @l having an annular externally threaded tubular portion 62 extending upwardly thereironi. rThe plug is also provided with an enlarged recess e3 through which the shaft 55 extends. A metal sleeve S. extends into the recess -53 and surrounds the shaft 55. The upper portion of the sleeve 6:2 has extending laterally and outwardly therefrom a contact arm te to which is detachably connected one end of a lead wire Se, as at t?. A tubular bushing e3 is positioned in the recess e3 between the sleeve et and the wall of the recess. Extending upwardly from the top of the annular portion 5?; of the plug 5i is a xed contact S9. The upper end of the shaft 55 terminates in an annular flange l@ which overlaps the contact te and constitutes a movable contact arranged to be brought in engagement with the nxed Contact es when the shaft is moved downwardly or further into the chamber l. A coil spring il is confined between the top of the bushing et and the flange le and tends to normall-y urge and maintain the movable contact away from the fixed contact S3. rlhe parts are enclosed in a removable cap '12 similar in construction to the cap lo previously described. Normally when the brake fluid e3 in the chamber Sil is at a level as indicated in Fig. 2, the neat 58 is buoyantly supported by the huid and is spaced from both the lower fla-nge 5e and the upper flange 5l. IThe outward tension oi the spring 'il now urges the contact l away from the contact til. However, the tension of the spring la' relative to the weight ol the float is such that, when the fluid 5t in the chamber s@ recedes or falls below a predetermined level, the float 53 will drop and engage the lower rlange 5B and the weight thereof will be sufficient to contract the spring li and move the contact '5e in engagement with the fixed contact 69 so as to establish an electrical circuit to a signal device, such as the light i3 previously described. Conversely, when lsulated member the chamber is replenished with nuid the float will move to the position as shown so as to be entirely supported by the iluid thus allowing the spring il to expand and move the Contact "it away from the contact S9.

In the modification shown in Fig. 5, the cylinder lt is provided with a brake fluid chamber 'iii having an opening EE closed by the removable plug le. A metal hollow rloat il' is arranged to float in the brake fluid 'ill in the chamber and has extending upwardly therefrom an operating shaft or stem it that extends loosely through a vertical opening Si) in the plug it, and terminates at its upper end in an annular ange or disk 3l that is arranged to constitute a removable electrical contact. An annular collar e2 is fixed to the shaft 'iQ and is positioned within the chamber so as to constitute a stop r'or limiting the upward axial movement of the shaft 2Q. A rubber gasket @3 may be interposed between the collar and the bottom of the plug le so as to provide a seal for closing the opening A fixed electrical contact S extends upwardly from the top of the plug 'it and is embedded in an int carried by a housing Se that is mounted in a fixed position on the topof the plug it in any suitable manner such as by welding ill. The housing has an open top which may be closed by a renie able lid 83 that nts in a reduced shoulder por n of the top or" the housing so as to be detachacly secured thereto in any suitable manner such as by the threaded bolts 3". rEhe upper portion or" ne shaft 'E9 and the movable contact 4 the housing to and the contact path of movement of the contact contact @Il has etxending outwardly and l orally therefrom an arm il@ to which a lead wire 9i may be dctachably connected as at A rubber gasket 93 may be interposed between the annular collar il@ on the plug l and i" top of cli@ the cylinder so as to provide a seal v hen the parts are assembled.

It will be seen that normally the brake iuid 'i8 in the chamber lil is at such a high level as to raise the shaft 'i9 so as to space the movable contact 3i away from its associated fixed contact Sii. When the brake fluid the chamber 'l recedes to a predetermined low level it will move the oat 'il' and shaft it downwardly, at the same time the Contact 8l is lnoved in engagement with the contacts 8d so as to establish an electrical circuit with a signal device such as the light i3 previously described.

It will be understood that the fori-ns or" the invention shown and described are merely illustrative and that such changes may oe made as come within the scope of the following claims.

I claim:

l. ln a hydraulic bralre system of the class described having in combination, a cylinder provided with an opening in the top thereof, a removable plug for closing said opening, said plug having a central aperture extending vertically therethrough, a reciprocating shaf t extending through said aperture into said chamber, a loat in said chamber, means connecting said float to one end of said shaft so tha the neat is axially slidable thereon, the opposite end or" said shaft extending above the plug and provided with a lateral projection constituting a movable electrical contact, a fixed electrical contact extending upwardly from the plug and below said projection so as to be engaged by the same when it is lowered, the top of the plug having an enlarged rcess concentric with said aperture, a tubular bushing mounted in said recess and enclosing said shaft, said bushing having an electrical contact extending radially and outwardly thereof, an insulated sleeve interposed between said bushing and the inner Wall of said recess, a coil spring surrounding said shaft and conned between said projection and said bushing for normally urging the shaft upwardly, and means for electrically connecting said contacts to a signal device so that normally the level of the brake fluid in said chamber supports the iloat and allows independent axial movement or" the shaft relative thereto, but when the brake fluid in said chamber recedes to a predetermined low level, the tension of the spring relative to the weight of the oat being such that the weight of the float on the shaft is suicient to overcome the upper tension of the spring so as to force the shaft downwardly and the movable contact in engagement with the iixed contact so as to close the circuit to the signal device.

2. In a hydraulic braking system of the class described having in combination, a cylinder provided with an opening in the top thereof, a removable plug for closing said opening, said plug having a central aperture extending vertically therethrough, a reciprocating shaft extending through said aperture into said chamber, a float in said chamber, means connecting said float to one end of said shaft so that the float is axially sldable thereon, the end of said shaft extending into the chamber having axially spaced anges, said float being slidably mounted on said Shaft between said flanges, the opposite end of said shaft extending above the plug and provided with 6 an annular collar constituting a movable contact, a fixed electrical contact extending upwardly from the plug and below said collar so as to be engaged by the collar when the latter is lowered, the top of the plug having an enlarged recess concentric with said aperture, a tubular bushing mounted in said recess and enclosing said shaft, said bushing constituting an electrical contact, an insulated sleeve interposed between said bushing and the inner wall of said recess, spring means on said shaft and connned between said collar and said bushing for normally urging the shaft upwardly, and means for electrically connecting said contacts to a signal device so that normally the upward tension of the spring means maintains the movable contact away from the fixed contact, the tension of the spring means relative to the weight of the float being such that said float upon receding of the brake iluid in the chamber below a predetermined level being moved downwardly in engagement with one of said anges so as to overcome the tension of the spring means and move the shaft axially to bring the movable contact in engagement with the ixed contact and close the circuit to the signal device.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 394,491 Johns Dec. 11, 1888 829,103 Dixon Aug. 21, 1906 1,497,712 Crandall et al June 17, 1924 1,759,503 Gerlach et al May 20, 1930 2,161,441 Vickers June 6, 1939 

